Fixture for grinding punches



June 9, 1964 J. G. HANNA 3,136,101

FIXTURE FOR GRINDING PUNCHES Filed April 29, 1965 \Q F\G.l FIG.2 IO

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JOHN G. HANNA r E 34 INVENTOR.

United States Patent 3,136,101 FIXTURE FOR GRINDING PUNCHES John G. Hanna, 230 E. Middle St., Chelsea, Mich. Filed Apr. 29, 1963, Ser. No. 276,513 1 (Ilaim. (Cl. 51217) This invention relates to fixtures for holding workpieces during machining, and particularly to fixtures for centering and holding punches during the grinding of flat surfaces thereon.

Punches are commonly used in dies to blank out holes of various shapes in metal stock, such holes frequently being round, rectangular, or square. The punch consists of a cylindrical shank bearing a working end closely ground to meet with the appropriate die and of a proper cross-sectional configuration to form the desired hole,

and bears at its upper end a head adapted to retain the punch in a punch holder. The head of the punch is customarily formed of sufficient breadth so as to retain the punch in a true position within the die holder at all times. Customarily, a pair of the edges of the head of the punch are ground flat and parallel to each other, and parallel also with a pair of the sides of the working end of the punch, so that the working end will be properly oriented when the punch is engaged within the punch holder. It is frequently necessary to grind a third edge of the head of the punch flat and disposed at a 90 angle to the pair of parallel edges, so that two punches may be positioned closely adjacent to each other within the punch holder.

The surface grinding of flat surfaces upon a cylindrical workpiece, to form the head and square or rectangular working part of a punch, is usually done by clamping the workpiece in a V-block with the portion to be ground projecting from one end of the block. The conventional V-block comprises a metal block having a V-shaped channel disposed to receive the workpiece longitudinally therein, and clamping means arranged to releasably retain the workpiece within said channel. The base of the conventional V-block is normal to the plane which bisects the V-shaped channel and is adapted to be chucked magnetically to a transversely adjustable table, whereby the workpiece may be presented to a grinding wheel for a desired grinding cut along a plane parallel to the base of the V-block.

In forming certain tools, such as a punch, it is often desired to grind one or more pairs of flat, parallel, opposing surfaces thereon equidistant from the longitudinal axis of the punch, to form a portion of the head, or a portion of the working part, or both, of the tool. Where a conventional V-block is used to hold the workpiece, it is necessary, after having ground one pair of flat, parallel, opposing surfaces to a measured depth in the workpiece, to remove the workpiece from the V-block and to rotate the workpiece 90 within the V-block until the pair of fiat surfaces thus ground are disposed precisely at a right angle to the base of the V-block, and to reclamp the workpiece within the V-block, before a second pair of flat, parallel, opposing surfaces may be ground at a right angle to said first pair. Further, with a conventional V-block, it is impossible to grind a first fiat surface in the workpiece, forming, say one side of the cutting portion, and subsequently to grind a second flat surface in the workpiece, parallel to said first surface, to form one side of, say, a head, without removing the workpiece from the V-block, since the configuration of a conventional V-block is such that a portion of it protrudes into the plane of such head and prevents contact of the grinding wheel with the portion of the workpiece from which a head must be formed. It is accordingly necessary to remove the workpiece from the V-block, and to re-position it and re-clamp it within the V-block for such purpose. Each time the workpiece is re-positioned within "ice the V-block, additional possibility of error is introduced.

It is accordingly an object of the present invention to provide an improved fixture for holding workpieces during machining operations thereon and adapted to permit a plurality of pairs of flat, parallel, opposing surfaces to be cut in said workpiece without the necessity of repositioning said workpiece within said fixture between the cutting of each pair of such surfaces.

A further object of the invention is to provide an improved fixture for grinding two pairs of flat, parallel surfaces on a cylindrical workpiece, said pairs being mutually arranged at a right angle to each other,-by rotating said fixture through, in turn, four positions of rest upon, respectively, four adjacent surfaces thereof arranged about a perimeter of the fixture in a plane normal to said longitudinal axis.

The above and other objects of the invention which will later become apparent as the following description proceeds, are attained by the present invention, a preferred embodiment of which has been illustrated, by way of example only, in the accompanying drawings, forming a part of this specification in which like characters are employed to designate like parts throughout the same, and wherein:

FIGURE 1 is a front elevation, partly in section, of a fixture holding a cylindrical workpiece centered therein.

FIGURE 2 is a side elevation of a fixture holding a cylindrical workpiece centered therein.

FIGURE 3 is a front elevation of a fixture holding a cylindrical workpiece of smaller diameter centered therein.

FIGURE 4 is a front elevation of a fixture holding a cylindrical workpiece centered therein with a partially formed working surface on said workpiece.

FIGURE 5 is a front elevation of a fixture rotated and holding a cylindrical workpiece centered therein with with a partially formed working surface on said workpiece.

FIGURE 7 is a front elevation of a fixture rotated 270 and holding a cylindrical workpiece centered therein with a rectangular working surface formed thereon.

FIGURE 8 is a rear elevation of a fixture rotated 270 and holding a cylindrical workpiece centered therein with a head formed thereon.

Referring now more particularly to the drawings, I first form a precisely square block 10 of steel. While block 10 may be of any desired size and thickness, I have found it convenient, for most applications of the invention, to use a block the length of each side of which is three inches and the thickness of which is three-quarters of an inch. A portion of the base 11 of block 10 is milled out to form a rectangular recess 12 having a uniform depth of preferably one-quarter inch therein. A rectangular heel block 14 is formed to fit snugly into recess 12, so that the inner face of the heel block rests fiat against the bottom of the recess and the outer face of the heel block is co-planar with the portions of the side of block 10 which flank the recess.

A pair of bores 16, 16 are then drilled in heel block 14 and block 10 near the ends of recess 12, and the portions of the bores extending within the block are tapped to receive a pair of countersunk flat head screws 18, 18 which retain the heel block firmly within the recess, as best shown in FIGURE 1. To insure that the base 11 of block 10 remains flat and parallel with the opposite side of the block, I remeasure the height of the block at several points with a micrometer at this stage of construction of the device, and, if necessary, grind down the outer surface of heel block 14 after it has been thus attached to block by screws 18, 18. When block 10, with heel block 14 attached, has been verified to be precisely square and all four sides thereof perfectly flat, construction of the device may proceed to the next stage.

With heel block 14 removed from block 10, a rectangular portion is cut and removed from block 10, extending upwardly from recess 12,to form a fixed rectangular jaw generally indicated at and having a pair of. fiat, parallel sides 22, 22 extending at right angles from, and one end 24 arranged precisely parallel to, base 11. Sides 22, 22 must be equidistant from and on opposite sides of the plane which bisects base 11 and is perpendicular thereto. The junctions of sides 22 with end 24 may be slightly rounded if preferred, but end 24 is fiat throughout substantially its entire length. I aw 20 may be formed to have any desired height and width, but I have found it convenient to form sides 22, 22 one inch apart and'end 24 two inches from base 11.

A sliding block 26 is then formed, having a thickness identical to that of block N, a width such as to form a sliding fit between sides 22, 22 and a V-shaped jaw 28 at the upper end thereof and arranged to be bisected by the plane which bisects base 11 and is perpendicular thereto, The two sides. of jaw 28 thus symmetrically arranged may be formed at any desired angle, less than 180, from each other. I have found it desirable, however, to dispose them apart an angular distance in excess of 45, and preferably in excess of 90. Sliding block 26 may be formed to have any desired height, but I have found it convenient to form it to have a height of seven-eighths of an inch so as to securely grip a cylindrical workpiece 30, having a diameter of one inch, when the sliding block is slightly elevated as hereinafter described. If desired, guide means may be provided, as by lugs (not shown) extending outwardly from the sides of block 26 and arranged to slide within longitudinal grooves (not shown) formed in sides 22, 22, respectively, so as to maintain block 26 co-planar with block 10 while permitting longitudinal sliding movement of block 26 within jaw 20.

A bore 32 is drilled and tapped through the center of heel block 14, extending upwardly within the plane perpendicularly bisecting base 11, to threadedly receive a screw 34 having a rounded upper end. An unthreaded bore 35, coaxial with but of a slightly greater diameter than bore 32, is drilled upwardly and extending a short distance into the bottom of sliding block 26. The upper, closed end of bore 35 is rounded to receive the rounded upper end of screw 34 therein and to freely permit rotation of the screw. An improved fixture 36 is thus formed.

In operation, with the device assembled and sliding block 26 resting atop heel block 14 and with screw 34 extending partially outward from base 11, the shank portion of a cylindrical workpiece, as cylindrical workpiece 3th, is inserted into jaw 20 with the two end portions thereof to be ground extending outwardly from the front and rear faces thereof. Screw 34 is then screwed into heel block 14 until it no longer extends outwardly be-' 2 FIGURE 1 and FIGURES 4 through 7, inclusive.

If the radius of the workpiece, as that of workpiece 30 shown in FIGURE 3, is not such that the workpiece will be precisely centered in fixture 36 when sliding block 26 is tightened thereagainst, a steel spacing block 46, of rectangular cross-section and having a thickness precisely,

equal to the difference between the radius of workpiece 30' and the distance from end 24 to the center of fixture 36 is inserted into the jaw between the workpiece and end 24, and sliding block 26 then tightened against the workpiece in the manner hereinbefore described. V-

shaped jaw 28 will cause workpiece 30' to be positioned so that its longitudinal axis lies equidistant from sides 22, 22 of jaw 20 and hence equidistant from the adjacent parallel sides of block 10; and spacing block 40 positions the longitudinal axis of workpiece equidistant from base 11 and the opposite, upper side of block 10. Workpiece 30 is thus precisely centered withinfixture 36.

I provide a plurality of spacing blocks for use with fixture 36, the several thicknesses thereof being such that, individually and in combination, they can be selected and utilized by an operator to center precisely any cylindrical workpiece 30' within fixture 36.

With workpiece 3i) centered in fixture 36, the fixture is chucked magnetically to an adjustable grinding table and a fiat surface 42 is ground in portion 38, parallel to one side of the fixture, as base 11, as best shown in FIGURE 4,'to form one side of a working end of a tool. Fixture 36 is then released from engagement with the grinding table, rotated 90, and again chucked magnetically to the grinding table with an adjacent side of the fixture in contact with the table, and a second flat surface 44 is ground therein, as best shown'in FIGURE 5. Fixture 36 is then again released from engagement with the grinding table, moved horizontally upon the table to a position such that the grinding wheel is disposed to contact portion 46 of workpiece 30 at the opposite end of the workpiece from portion 38 and extending outwardly from the rear of fixture 36, and the fixture is then again chucked magnetically to the grinding table. A fiat surface 48 is then ground in portion 46 of workpiece 36 to form one flat edge of a head of a tool. Since workpiece 39 has not been removed from fixture 36, surfaces 44 and 48 will be precisely parallel to each other and, since fixture 36 is precisely square, surfaces 44 and 48 will be formed precisely at a right angle to surface 42.

Fixture 36 is then again released from engagement with the grinding table, rotated another 90, and again chucked magnetically to the grinding tablewith the side of the fixture opposite base 11 in contact with the table and with portion 38 of workpiece 30 disposed to be contacted by the grinding wheel, as best shown in FIGURE 6. Another fiat surface 50 is then ground in portion 38 which, since fixture 36 is precisely square and the workpiece has not been repositioned therein, will be precisely parallel to surface 42 and formed at a precise right angle to surface 44. In a similar manner fixture, 36 is then rotated another 90 and rechucked upon the magnetic table, first in a position, as best shown in FIGURE 7, such that a fiat surface 52 may be ground in portion 38 of workpiece 30, and, secondly, in a position, as best shown in FIGURE 8, such that a second flat surface 54 may be ground in portion 46 of. the workpiece; both precisely parallel to surfaces 44 and 48 and at a precise right angle to surfaces 42 and 50.

Flat surfaces 42, 44, 50 and 52 thus form the sides of a precisely rectangular working end 56 of a tool, and surfaces 48 and 54 thus form two flat, parallel sides of a head 58 of such tool, said flat sides of said head being precisely parallel with parallel, opposite sides 44 and 52 of the working portion of the tool. It should be particularly noted that workpiece 30 does not have to be rotated-within fixture 36, and that the uniform thickness of the fixture allows both the working surface and the head of the tool to be formed without reversing the position of the workpiece within the fixture. Thus up to four pair of fiat, parallel surfaces can be conveniently ground in the cylindrical workpiece, one set of four forming a precisely rectangular working surface and the other set of four forming a precisely rectangular head, if desired, both sets being precisely parallel with each other.

It should be noted that, since the cylindrical workpiece is precisely centered in fixture 36, the longitudinal axis of the workpiece will be supported by the fixture at a uniform height above the grinding table in each of the four positions assumed by the fixture, and rectangular working end 50 and head 58 thus ground will be symmetrical about said axis. By grinding each flat surface to the same depth, working end 50 may be formed to be a square. If desired, however, each flat surface 42, 44, 50 and 52 may be ground to a different depth, so as to dispose rectangular Working end 50 off-center from the longitudinal axis of workpiece 30.

What is claimed is:

A fixture for centering, clamping, and disposing of a cylindrical workpiece for the grinding of a plurality of pairs of fiat, parallel surfaces thereon and comprising, a precisely square block of uniform thickness, an elongated, rectangular fixed jaw in said block, said jaw having an end arranged parallel to the base of said block and disposed between the center of said block and the side thereof opposite said base, the sides of said jaw being mutually parallel and arranged at a right angle to said base and symmetrically equidistant from and on opposite sides of an axis of said block, said end and sides, respectively, be

ing spaced equidistant from the proximate sides of said block, a heel block recessed in the base of said block, a sliding block having a V-shaped jaw and arranged for longitudinal sliding movement within said fixed jaw and between the sides thereof, said V-shaped jaw being arranged symmetrically with respect to and bisected by said axis of said block and disposed to center said workpiece with respect to said axis, and a screw extending through and threadably engaged with said heel block and adapted to force said sliding block in the direction of said end and against said workpiece, to center said workpiece with respect to the axis of said square block transverse to said first axis, and to clamp said workpiece Within said square block.

References Cited in the file of this patent UNITED STATES PATENTS 2,194,089 Iohns'on Mar. 19, 1940 2,353,131 Ford July 11, 1944 2,544,097 Lentz Mar. 6, 1951 2,585,594 Snyder Feb. 12, 1952 2,718,104 Kirklin Sept. 20, 1955 3,094,821 Eckert June 25, 1963 FOREIGN PATENTS 955,203 Germany Dec. 27, 1956 

